DIY Kayak Cart

Any DIYers who can give me some advice on a cart I’m trying to build (see attached picture)?

It’s actually for a 40″ wide fishing SUP with a transom mount trolling motor and swivel seat. With battery, I’ve got a total weight of just under 120 lbs.

1. Will 3/8″ threaded steel axle be strong enough to support 120-150 lbs or do I need to upsize?

2. How can I best secure the PVC cover on either end of the axle, so that it does not slide around? Lock nuts? Drill+cotter pin? Some kind of PVC insert?

3. For the quick release wheels, I’m hoping to use 3/8″ plastic star nuts like this:

https://www.imperialsupplies.com/item/9196467

This is an attempt to duplicate the effective but cheaply built cart that comes from the manufacturer, but with 20″ wheels instead of the plastic 14″ lawn mower wheels it comes with.

Any advice much appreciated!

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Nice, that is the best YouTube I’ve seen yet that is close to what I’m after, and it definitely gives me ideas.

My only potential issues with that build are that it may more heavy-duty than I need (although I’m now thinking 3/8″ bar may not be enough on its own), but more importantly, I need a method for easy quick release wheels vs. his permanent cotter pins.

But this is getting me closer, thanks!

Edit to add: was just reading the comments from that video, and people are using trailer hitch pins so it looks like this may actually be perfect.

UTUBE has a ton of builds. A used deer cart for $30 or $50 can save you a ton over hardware or homecenter. Has most of what you need in a proper weight rating. This is the hitch pin I use for most everything.

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I have a SOT Fishing Kayak which goes about 110 with the things I’ve added. I did a PVC build with a threaded rod axel. I will say that if you’re only going to use at boat ramps, a PVC build works fine. But if you ever take it on rougher terrain like a trail with roots and logs, the PVC will eventually fail. Had this happen to me. I ended up buying a cart in the end.

But not knocking a homebuilt job, just have to build it for the way you plan to use it. Scupper carts are tough to get the pegs in the holes without tipping your yak over, and when you have semi-attached accessories, etc. that gets to be a pain.

I have a Hobie scupper cart. Most of this stuff is bungeed in, because after time I’ve had to roll it on its side to remove the cart. When it was new, I could pick up one end and it would drop out. Not so much a problem with things falling out. Don’t like rolling it on concrete ramps. I’m going to have a second option this year.
Also think of what surface you will be pulling it on most. One spot I fish is a smooth packed gravel service road that’s near a mile long. In Florida it’s usually sand. Two completely different tires. Bicycle tires will sink in sand and mud, beach tires won’t last on gravel or concrete.

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I tried to find the old pics to scan of the ones we built when we did canoeing trips in the boundary waters. Very similar to the YouTube video posted. For our canoes and gear, we liked the rims/tires we harvested from old 10speed touring bikes. The taller the tires the easier it was.

We also had extra ratchet straps for breaking them down and portages